Revenue passenger-miles are a measure of the volume of air passenger transportation. Unused seat-miles (the difference between available seat-miles and revenue passenger miles) are used as a measure of airline capacity utilization. Another measure is the intensity of use of
the equipment.

NOTE: A revenue passenger-mile is equal to one paying passenger carried one mile. Available seat-miles for an individual flight are the number of seats multiplied by the distance traveled. The data include both transborder and foreign flights by large U.S. carriers, but not include any flights by
foreign carriers.

Domestic Passenger Aviation

Apr-02

Apr-03

Available seat-miles (billions)

55.60

51.93

Percent change from same month previous year

-8.09

-6.60

Revenue passenger-miles (billions)

39.53

37.76

Percent change from same month previous year

-9.57

-4.48

Unused seat-miles (billions)

16.07

14.17

Percent change from same month previous year

-4.23

-11.80

NOTES: The current value is compared to the value from the same period in the previous year to account for seasonality. The data have been adjusted to have a standard 30-day month by multiplying the data for each month by the
ratio: 30/(actual days in month).

These indicators are components of the passenger and overall aircraft load factors displayed in "Aircraft Utilization-Passengers
and Freight."

The dramatic changes in the September 2001 data reflect the impact of the terrorist attacks on Sept. 11, 2001, on aviation, including several days in which commercial air operations were
suspended.

The data reported here excludes small-certificated and commuter carriers that began reporting T100 data in 2002 for comparability with
previous issue.

Refer to the Special Notes at
http://www.bts.gov/oai/ for specific concerns regarding the preliminary nature of the most recent data for latest issue of Air Carrier Traffic
Statistic Monthly.

SOURCE: U.S. Department of Transportation, Bureau of Transportation Statistics, Air Carrier Traffic Statistics
Monthly, April 2003.